The 15-LO cascade is implicated in various inflammatory disorders, including disorders involving the origin and recruitment of foam cells. Cholesterol is transported in blood particles called lipoproteins, which include low-density lipoproteins (LDL). Lipoproteins contain cholesterol and are necessary for foam cell formation. The formation of foam cells can lead to serious disorders. For example, hypercholesterolemia can induce monocytes to migrate into the arterial wall and mature into foam cells or tissue macrophages that accumulate fatty material, including cholesterol esters. Continued creation of foam cells thickens the inner lining of medium and large arteries, thereby forming atherosclerotic plaques or lesions containing cholesterol, smooth muscle cells, and connective tissue cells. Affected arteries lose elasticity and become narrowed or obstructed by the plaques indicating the onset of atherosclerosis. Atherosclerotic plaques may collect calcium, become brittle, and even rupture triggering the formation of a blood clot or thrombus capable of occluding an artery and causing a stroke or heart attack. In addition to atherosclerosis, hypercholesteremia plays a role in peripheral vascular diseases of small arteries, veins and lymphatics. Thus, hypercholesteremia may also affect the arms, legs, kidneys and other vital organs in addition to the heart and brain.
Lipoxygenases are enzymes that catalyze the oxidation of polyunsaturated fatty acids and esters thereof, including those found in low-density lipoproteins. In addition to metabolism of free fatty acids, the enzyme 15-lipoxygenase (15-LO) also oxidizes esterified polyenoic fatty acids. Related to its general pathology, it is believed that oxidative metabolites of the 15-LO cascade [e.g. the arachidonic acid metabolite 15-hydroperoxyeicosatetraenoic acid (15-HPETE)], induce endothelial cell activation and subsequent adhesion molecule expression resulting in monocyte recruitment to the vessel wall [Sultana et al, J. of Cellular Physiology 167 (1996) 467-487]. 15-Hydroxyeicosatetraenoic acid (15-HETE), a reduction product of 15-HPETE, has also been implicated in the potentiation of thrombin-induced platelet activation [Setty et al, Blood, 80:11 (1992): 2765-2773]. It has also been demonstrated that arachidonic acid metabolites of the 15-LO cascade, namely 15-hydroperoxyeicosatetraenoic acid (15-HPETE), induce a pro-thrombotic state in endothelial cells through enhancement of plasminogen activator inhibitor-1 (PAI-1) release. Additionally, evidence that 15-LO is involved in the pathology of diabetes, it has been demonstrated that deletion of the mouse gene homologue of 15-LO leads to a reduction of disease progression [Bleich et al, J Clin Invest (1999) May 15;103(10):1431-6]. 15-LO has also been implicated in the progression of various cancers [Kelavkar et al, Curr Urol Rep 2002 Jun.; 3(3):207-14]. Not only in the progression of the cancer itself, but also in its related pathologies including cachexia and wasting [Tisdale et al, Science 2000 Sep. 29;289(5488):2293-4].
Inhibition of 15-LO, therefore, would be useful to prevent and treat diseases with either an inflammatory component, a thrombotic component, or both as in the case of atherosclerosis, as well as various cancers. For example, it has been shown that treatment with a 15-LO inhibitor suppressed atherogenesis (or the production of atheroma—a fatty degeneration of the arterial wall) in rabbits fed a high-fat diet [Bocan et al, Atherosclerosis, 136 (1998): 203-216]. Additional diseases in which treatment with a 15-LO inhibitor would be useful include asthma, psoriasis, osteoarthritis, rheumatoid arthritis, Alzheimer's disease, and chronic obstructive pulmonary disease.